The remarks follow weeks of chilling testimony in a Massachusetts courthouse about murders and other crimes attributed to Bulger. The defense has questioned the credibility of the government’s key witnesses, saying jurors can’t believe them beyond a reasonable doubt.

Bulger, 83, is charged with 19 murders as well as extortion, money laundering and arms trafficking. He was arrested in California in 2011 after spending 16 years on the run.

“The Winter Hill gang and the Mafia acted as judge, jury and sometimes executioners in any dispute. They act as the law in the criminal world,” prosecutor Fred Wyshak said of the group Bulger ran.

“The evidence in this case is overwhelming. As leader, he is legally responsible for it all,” the lawyer said.

Prosecutors called 63 witnesses in the trial that began June 4. Some recounted harrowing tales of murder victims having their teeth removed to block posthumous identification and a mobster’s girlfriend being strangled to death because she “knew too much.”